//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "liveintervals"
-#include "llvm/CodeGen/LiveIntervals.h"
+#include "LiveIntervals.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "Support/CommandLine.h"
#include "Support/Debug.h"
#include "Support/Statistic.h"
+#include "Support/STLExtras.h"
+#include "VirtRegMap.h"
#include <cmath>
#include <iostream>
#include <limits>
RegisterAnalysis<LiveIntervals> X("liveintervals",
"Live Interval Analysis");
- Statistic<> numIntervals("liveintervals", "Number of intervals");
- Statistic<> numJoined ("liveintervals", "Number of joined intervals");
+ Statistic<> numIntervals
+ ("liveintervals", "Number of original intervals");
+
+ Statistic<> numIntervalsAfter
+ ("liveintervals", "Number of intervals after coalescing");
+
+ Statistic<> numJoins
+ ("liveintervals", "Number of interval joins performed");
+
+ Statistic<> numPeep
+ ("liveintervals", "Number of identity moves eliminated after coalescing");
+
+ Statistic<> numFolded
+ ("liveintervals", "Number of loads/stores folded into instructions");
cl::opt<bool>
join("join-liveintervals",
{
mbbi2mbbMap_.clear();
mi2iMap_.clear();
- r2iMap_.clear();
+ i2miMap_.clear();
r2iMap_.clear();
r2rMap_.clear();
intervals_.clear();
/// runOnMachineFunction - Register allocate the whole function
///
bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
- DEBUG(std::cerr << "Machine Function\n");
mf_ = &fn;
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
- inserted = mi2iMap_.insert(std::make_pair(*mi, miIndex)).second;
+ inserted = mi2iMap_.insert(std::make_pair(mi, miIndex)).second;
assert(inserted && "multiple MachineInstr -> index mappings");
- miIndex += 2;
+ i2miMap_.push_back(mi);
+ miIndex += InstrSlots::NUM;
}
}
computeIntervals();
- // compute spill weights
+ numIntervals += intervals_.size();
+
+ // join intervals if requested
+ if (join) joinIntervals();
+
+ numIntervalsAfter += intervals_.size();
+
+ // perform a final pass over the instructions and compute spill
+ // weights, coalesce virtual registers and remove identity moves
const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
const TargetInstrInfo& tii = tm_->getInstrInfo();
- for (MachineFunction::const_iterator mbbi = mf_->begin(),
- mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
- const MachineBasicBlock* mbb = mbbi;
+ for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
+ mbbi != mbbe; ++mbbi) {
+ MachineBasicBlock* mbb = mbbi;
unsigned loopDepth = loopInfo.getLoopDepth(mbb->getBasicBlock());
- for (MachineBasicBlock::const_iterator mii = mbb->begin(),
- mie = mbb->end(); mii != mie; ++mii) {
- MachineInstr* mi = *mii;
+ for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
+ mii != mie; ) {
+ for (unsigned i = 0; i < mii->getNumOperands(); ++i) {
+ const MachineOperand& mop = mii->getOperand(i);
+ if (mop.isRegister() && mop.getReg()) {
+ // replace register with representative register
+ unsigned reg = rep(mop.getReg());
+ mii->SetMachineOperandReg(i, reg);
+
+ if (MRegisterInfo::isVirtualRegister(reg)) {
+ Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
+ assert(r2iit != r2iMap_.end());
+ r2iit->second->weight += pow(10.0F, loopDepth);
+ }
+ }
+ }
- for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
- MachineOperand& mop = mi->getOperand(i);
- if (mop.isVirtualRegister()) {
- unsigned reg = mop.getAllocatedRegNum();
- Reg2IntervalMap::iterator r2iit = r2iMap_.find(reg);
- assert(r2iit != r2iMap_.end());
- r2iit->second->weight += pow(10.0F, loopDepth);
+ // if the move is now an identity move delete it
+ unsigned srcReg, dstReg;
+ if (tii.isMoveInstr(*mii, srcReg, dstReg) && srcReg == dstReg) {
+ // remove index -> MachineInstr and
+ // MachineInstr -> index mappings
+ Mi2IndexMap::iterator mi2i = mi2iMap_.find(mii);
+ if (mi2i != mi2iMap_.end()) {
+ i2miMap_[mi2i->second/InstrSlots::NUM] = 0;
+ mi2iMap_.erase(mi2i);
}
+ mii = mbbi->erase(mii);
+ ++numPeep;
}
+ else
+ ++mii;
}
}
- // join intervals if requested
- if (join) joinIntervals();
-
- numIntervals += intervals_.size();
-
intervals_.sort(StartPointComp());
+ DEBUG(std::cerr << "********** INTERVALS **********\n");
DEBUG(std::copy(intervals_.begin(), intervals_.end(),
std::ostream_iterator<Interval>(std::cerr, "\n")));
+ DEBUG(std::cerr << "********** MACHINEINSTRS **********\n");
+ DEBUG(
+ for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
+ mbbi != mbbe; ++mbbi) {
+ std::cerr << mbbi->getBasicBlock()->getName() << ":\n";
+ for (MachineBasicBlock::iterator mii = mbbi->begin(),
+ mie = mbbi->end(); mii != mie; ++mii) {
+ std::cerr << getInstructionIndex(mii) << '\t';
+ mii->print(std::cerr, *tm_);
+ }
+ });
+
return true;
}
+void LiveIntervals::updateSpilledInterval(Interval& li,
+ VirtRegMap& vrm,
+ int slot)
+{
+ assert(li.weight != std::numeric_limits<float>::infinity() &&
+ "attempt to spill already spilled interval!");
+ Interval::Ranges oldRanges;
+ swap(oldRanges, li.ranges);
+
+ DEBUG(std::cerr << "\t\t\t\tupdating interval: " << li);
+
+ for (Interval::Ranges::iterator i = oldRanges.begin(), e = oldRanges.end();
+ i != e; ++i) {
+ unsigned index = getBaseIndex(i->first);
+ unsigned end = getBaseIndex(i->second-1) + InstrSlots::NUM;
+ for (; index < end; index += InstrSlots::NUM) {
+ // skip deleted instructions
+ while (!getInstructionFromIndex(index)) index += InstrSlots::NUM;
+ MachineBasicBlock::iterator mi = getInstructionFromIndex(index);
+
+ for_operand:
+ for (unsigned i = 0; i < mi->getNumOperands(); ++i) {
+ MachineOperand& mop = mi->getOperand(i);
+ if (mop.isRegister() && mop.getReg() == li.reg) {
+ if (MachineInstr* fmi =
+ mri_->foldMemoryOperand(mi, i, slot)) {
+ lv_->instructionChanged(mi, fmi);
+ vrm.virtFolded(li.reg, mi, fmi);
+ mi2iMap_.erase(mi);
+ i2miMap_[index/InstrSlots::NUM] = fmi;
+ mi2iMap_[fmi] = index;
+ MachineBasicBlock& mbb = *mi->getParent();
+ mi = mbb.insert(mbb.erase(mi), fmi);
+ ++numFolded;
+ goto for_operand;
+ }
+ else {
+ // This is tricky. We need to add information in
+ // the interval about the spill code so we have to
+ // use our extra load/store slots.
+ //
+ // If we have a use we are going to have a load so
+ // we start the interval from the load slot
+ // onwards. Otherwise we start from the def slot.
+ unsigned start = (mop.isUse() ?
+ getLoadIndex(index) :
+ getDefIndex(index));
+ // If we have a def we are going to have a store
+ // right after it so we end the interval after the
+ // use of the next instruction. Otherwise we end
+ // after the use of this instruction.
+ unsigned end = 1 + (mop.isDef() ?
+ getUseIndex(index+InstrSlots::NUM) :
+ getUseIndex(index));
+ li.addRange(start, end);
+ }
+ }
+ }
+ }
+ }
+ // the new spill weight is now infinity as it cannot be spilled again
+ li.weight = std::numeric_limits<float>::infinity();
+ DEBUG(std::cerr << '\n');
+ DEBUG(std::cerr << "\t\t\t\tupdated interval: " << li << '\n');
+}
+
void LiveIntervals::printRegName(unsigned reg) const
{
if (MRegisterInfo::isPhysicalRegister(reg))
std::cerr << mri_->getName(reg);
else
- std::cerr << '%' << reg;
+ std::cerr << "%reg" << reg;
}
void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
unsigned reg)
{
- DEBUG(std::cerr << "\t\tregister: ";printRegName(reg); std::cerr << '\n');
-
+ DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
LiveVariables::VarInfo& vi = lv_->getVarInfo(reg);
Interval* interval = 0;
if (vi.AliveBlocks[i]) {
MachineBasicBlock* mbb = lv_->getIndexMachineBasicBlock(i);
if (!mbb->empty()) {
- interval->addRange(getInstructionIndex(mbb->front()),
- getInstructionIndex(mbb->back()) + 1);
+ interval->addRange(
+ getInstructionIndex(&mbb->front()),
+ getInstructionIndex(&mbb->back()) + InstrSlots::NUM);
}
}
}
interval = &*r2iit->second;
}
- // we consider defs to happen at the second time slot of the
- // instruction
- unsigned instrIndex = getInstructionIndex(*mi) + 1;
+ unsigned baseIndex = getInstructionIndex(mi);
bool killedInDefiningBasicBlock = false;
for (int i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineBasicBlock* killerBlock = vi.Kills[i].first;
MachineInstr* killerInstr = vi.Kills[i].second;
unsigned start = (mbb == killerBlock ?
- instrIndex :
- getInstructionIndex(killerBlock->front()));
- unsigned end = (killerInstr == *mi ?
- instrIndex + 1 : // dead
- getInstructionIndex(killerInstr) + 1); // killed
+ getDefIndex(baseIndex) :
+ getInstructionIndex(&killerBlock->front()));
+ unsigned end = (killerInstr == mi ?
+ // dead
+ start + 1 :
+ // killed
+ getUseIndex(getInstructionIndex(killerInstr))+1);
// we do not want to add invalid ranges. these can happen when
// a variable has its latest use and is redefined later on in
// the same basic block (common with variables introduced by
}
if (!killedInDefiningBasicBlock) {
- unsigned end = getInstructionIndex(mbb->back()) + 1;
- interval->addRange(instrIndex, end);
+ unsigned end = getInstructionIndex(&mbb->back()) + InstrSlots::NUM;
+ interval->addRange(getDefIndex(baseIndex), end);
}
+ DEBUG(std::cerr << '\n');
}
void LiveIntervals::handlePhysicalRegisterDef(MachineBasicBlock* mbb,
MachineBasicBlock::iterator mi,
unsigned reg)
{
- typedef LiveVariables::killed_iterator KillIter;
-
DEBUG(std::cerr << "\t\tregister: "; printRegName(reg));
+ typedef LiveVariables::killed_iterator KillIter;
MachineBasicBlock::iterator e = mbb->end();
- // we consider defs to happen at the second time slot of the
- // instruction
- unsigned start, end;
- start = end = getInstructionIndex(*mi) + 1;
+ unsigned baseIndex = getInstructionIndex(mi);
+ unsigned start = getDefIndex(baseIndex);
+ unsigned end = start;
// a variable can be dead by the instruction defining it
- for (KillIter ki = lv_->dead_begin(*mi), ke = lv_->dead_end(*mi);
+ for (KillIter ki = lv_->dead_begin(mi), ke = lv_->dead_end(mi);
ki != ke; ++ki) {
if (reg == ki->second) {
- DEBUG(std::cerr << " dead\n");
- ++end;
+ DEBUG(std::cerr << " dead");
+ end = getDefIndex(start) + 1;
goto exit;
}
}
// a variable can only be killed by subsequent instructions
do {
++mi;
- end += 2;
- for (KillIter ki = lv_->killed_begin(*mi), ke = lv_->killed_end(*mi);
+ baseIndex += InstrSlots::NUM;
+ for (KillIter ki = lv_->killed_begin(mi), ke = lv_->killed_end(mi);
ki != ke; ++ki) {
if (reg == ki->second) {
- DEBUG(std::cerr << " killed\n");
+ DEBUG(std::cerr << " killed");
+ end = getUseIndex(baseIndex) + 1;
goto exit;
}
}
r2iMap_.insert(r2iit, std::make_pair(reg, --intervals_.end()));
intervals_.back().addRange(start, end);
}
+ DEBUG(std::cerr << '\n');
}
void LiveIntervals::handleRegisterDef(MachineBasicBlock* mbb,
unsigned LiveIntervals::getInstructionIndex(MachineInstr* instr) const
{
- assert(mi2iMap_.find(instr) != mi2iMap_.end() &&
- "instruction not assigned a number");
- return mi2iMap_.find(instr)->second;
+ Mi2IndexMap::const_iterator it = mi2iMap_.find(instr);
+ return (it == mi2iMap_.end() ?
+ std::numeric_limits<unsigned>::max() :
+ it->second);
+}
+
+MachineInstr* LiveIntervals::getInstructionFromIndex(unsigned index) const
+{
+ index /= InstrSlots::NUM; // convert index to vector index
+ assert(index < i2miMap_.size() &&
+ "index does not correspond to an instruction");
+ return i2miMap_[index];
}
/// computeIntervals - computes the live intervals for virtual
/// which a variable is live
void LiveIntervals::computeIntervals()
{
- DEBUG(std::cerr << "computing live intervals:\n");
+ DEBUG(std::cerr << "********** COMPUTING LIVE INTERVALS **********\n");
+ DEBUG(std::cerr << "********** Function: "
+ << mf_->getFunction()->getName() << '\n');
for (MbbIndex2MbbMap::iterator
it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
it != itEnd; ++it) {
MachineBasicBlock* mbb = it->second;
- DEBUG(std::cerr << "machine basic block: "
- << mbb->getBasicBlock()->getName() << "\n");
+ DEBUG(std::cerr << mbb->getBasicBlock()->getName() << ":\n");
for (MachineBasicBlock::iterator mi = mbb->begin(), miEnd = mbb->end();
mi != miEnd; ++mi) {
- MachineInstr* instr = *mi;
const TargetInstrDescriptor& tid =
- tm_->getInstrInfo().get(instr->getOpcode());
- DEBUG(std::cerr << "\t[" << getInstructionIndex(instr) << "] ";
- instr->print(std::cerr, *tm_););
+ tm_->getInstrInfo().get(mi->getOpcode());
+ DEBUG(std::cerr << getInstructionIndex(mi) << "\t";
+ mi->print(std::cerr, *tm_));
// handle implicit defs
for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
handleRegisterDef(mbb, mi, *id);
// handle explicit defs
- for (int i = instr->getNumOperands() - 1; i >= 0; --i) {
- MachineOperand& mop = instr->getOperand(i);
+ for (int i = mi->getNumOperands() - 1; i >= 0; --i) {
+ MachineOperand& mop = mi->getOperand(i);
// handle register defs - build intervals
- if (mop.isRegister() && mop.isDef())
- handleRegisterDef(mbb, mi, mop.getAllocatedRegNum());
+ if (mop.isRegister() && mop.getReg() && mop.isDef())
+ handleRegisterDef(mbb, mi, mop.getReg());
}
}
}
void LiveIntervals::joinIntervals()
{
- DEBUG(std::cerr << "joining compatible intervals:\n");
+ DEBUG(std::cerr << "********** JOINING INTERVALS ***********\n");
const TargetInstrInfo& tii = tm_->getInstrInfo();
- for (MachineFunction::const_iterator mbbi = mf_->begin(),
- mbbe = mf_->end(); mbbi != mbbe; ++mbbi) {
- const MachineBasicBlock* mbb = mbbi;
- DEBUG(std::cerr << "machine basic block: "
- << mbb->getBasicBlock()->getName() << "\n");
+ for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end();
+ mbbi != mbbe; ++mbbi) {
+ MachineBasicBlock* mbb = mbbi;
+ DEBUG(std::cerr << mbb->getBasicBlock()->getName() << ":\n");
- for (MachineBasicBlock::const_iterator mii = mbb->begin(),
- mie = mbb->end(); mii != mie; ++mii) {
- MachineInstr* mi = *mii;
+ for (MachineBasicBlock::iterator mi = mbb->begin(), mie = mbb->end();
+ mi != mie; ++mi) {
const TargetInstrDescriptor& tid =
tm_->getInstrInfo().get(mi->getOpcode());
- DEBUG(std::cerr << "\t\tinstruction["
- << getInstructionIndex(mi) << "]: ";
+ DEBUG(std::cerr << getInstructionIndex(mi) << '\t';
mi->print(std::cerr, *tm_););
// we only join virtual registers with allocatable
r2iB->second = r2iA->second;
r2rMap_.insert(std::make_pair(intB->reg, intA->reg));
intervals_.erase(intB);
- ++numJoined;
}
}
else if (MRegisterInfo::isPhysicalRegister(intA->reg) ^
r2iB->second = r2iA->second;
r2rMap_.insert(std::make_pair(intB->reg, intA->reg));
intervals_.erase(intB);
- ++numJoined;
}
}
}
LiveIntervals::Interval::Interval(unsigned r)
: reg(r),
weight((MRegisterInfo::isPhysicalRegister(r) ?
- std::numeric_limits<float>::max() : 0.0F))
+ std::numeric_limits<float>::infinity() : 0.0F))
{
}
+bool LiveIntervals::Interval::spilled() const
+{
+ return (weight == std::numeric_limits<float>::infinity() &&
+ MRegisterInfo::isVirtualRegister(reg));
+}
+
// An example for liveAt():
//
-// this = [1,2), liveAt(0) will return false. The instruction defining
-// this spans slots [0,1]. Since it is a definition we say that it is
-// live in the second slot onwards. By ending the lifetime of this
-// interval at 2 it means that it is not used at all. liveAt(1)
-// returns true which means that this clobbers a register at
-// instruction at 0.
+// this = [1,4), liveAt(0) will return false. The instruction defining
+// this spans slots [0,3]. The interval belongs to an spilled
+// definition of the variable it represents. This is because slot 1 is
+// used (def slot) and spans up to slot 3 (store slot).
//
-// this = [1,4), liveAt(0) will return false and liveAt(2) will return
-// true. The variable is defined at instruction 0 and last used at 2.
bool LiveIntervals::Interval::liveAt(unsigned index) const
{
Range dummy(index, index+1);
// An example for overlaps():
//
// 0: A = ...
-// 2: B = ...
-// 4: C = A + B ;; last use of A
+// 4: B = ...
+// 8: C = A + B ;; last use of A
//
// The live intervals should look like:
//
-// A = [1, 5)
-// B = [3, x)
-// C = [5, y)
+// A = [3, 11)
+// B = [7, x)
+// C = [11, y)
//
// A->overlaps(C) should return false since we want to be able to join
// A and C.
void LiveIntervals::Interval::addRange(unsigned start, unsigned end)
{
assert(start < end && "Invalid range to add!");
- DEBUG(std::cerr << "\t\t\tadding range: [" << start <<','<< end << ") -> ");
+ DEBUG(std::cerr << " +[" << start << ',' << end << ")");
//assert(start < end && "invalid range?");
Range range = std::make_pair(start, end);
Ranges::iterator it =
it = mergeRangesForward(it);
it = mergeRangesBackward(it);
- DEBUG(std::cerr << "\t\t\t\tafter merging: " << *this << '\n');
}
void LiveIntervals::Interval::join(const LiveIntervals::Interval& other)
{
- DEBUG(std::cerr << "\t\t\t\tjoining intervals: "
- << other << " and " << *this << '\n');
+ DEBUG(std::cerr << "\t\tjoining " << *this << " with " << other << '\n');
Ranges::iterator cur = ranges.begin();
for (Ranges::const_iterator i = other.ranges.begin(),
cur = mergeRangesForward(cur);
cur = mergeRangesBackward(cur);
}
- if (MRegisterInfo::isVirtualRegister(reg))
- weight += other.weight;
-
- DEBUG(std::cerr << "\t\t\t\tafter merging: " << *this << '\n');
+ weight += other.weight;
+ ++numJoins;
}
LiveIntervals::Interval::Ranges::iterator
LiveIntervals::Interval::mergeRangesForward(Ranges::iterator it)
{
- for (Ranges::iterator next = it + 1;
- next != ranges.end() && it->second >= next->first; ) {
- it->second = std::max(it->second, next->second);
- next = ranges.erase(next);
+ Ranges::iterator n;
+ while ((n = next(it)) != ranges.end()) {
+ if (n->first > it->second)
+ break;
+ it->second = std::max(it->second, n->second);
+ n = ranges.erase(n);
}
return it;
}
LiveIntervals::Interval::mergeRangesBackward(Ranges::iterator it)
{
while (it != ranges.begin()) {
- Ranges::iterator prev = it - 1;
- if (it->first > prev->second) break;
+ Ranges::iterator p = prior(it);
+ if (it->first > p->second)
+ break;
- it->first = std::min(it->first, prev->first);
- it->second = std::max(it->second, prev->second);
- it = ranges.erase(prev);
+ it->first = std::min(it->first, p->first);
+ it->second = std::max(it->second, p->second);
+ it = ranges.erase(p);
}
return it;
const LiveIntervals::Interval& li)
{
os << "%reg" << li.reg << ',' << li.weight << " = ";
+ if (li.empty())
+ return os << "EMPTY";
for (LiveIntervals::Interval::Ranges::const_iterator
i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
os << "[" << i->first << "," << i->second << ")";
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